Process for hydrolyzing 7-aminocephalosporanic acid lactone

ABSTRACT

Desacetyl 7-aminocephalosporanic acid is obtained chemically in reasonable yield from desacetyl 7-aminocephalosporanic acid lactone by subjecting the lactone in a basic water-containing medium to a pH of 11-13 for 5 seconds to 5 minutes.

United States Patent Constantino John Di Cuollo Drexel Hill;

George L. Dunn, Wayne; Louis R. Fare, La Fayette Hill, all of Pa.

Nov. 1 7, 1969 Sept. 21, 1971 Smith Kline & French Laboratories Philadelphia, Pa.

[72] Inventors [21 Appl. No. [22] Filed [45] Patented [73] Assignee 54 PROCESS FOR HRDROLYZING 7- AMINOCEPHALOSPORANIC ACID LACTONE 4 Claims, No Drawings 52 U.S. c1 260/243 51 1m.c| ..C07d99/24 Primary ExaminerNicholas S. Rizzo Attorneys-William H. Edgerton, Richard D. Foggio, Joan S.

Keps, Alan D. Lourie and Joseph A. Marlino ABSTRACT: Desacetyl 7-aminocephalosporanic acid is obtained chemically in reasonable yield from desacetyl 7- aminocephalosporanic acid lactone by subjecting the lactone in a basic water-containing medium to a pH of ll-l3 for 5 seconds to 5' minutes.

I COOH The amino group of alcohol I can be acylated by known' methods with any of a number of known-acylating agents to produce desacetyl cephalosporins; which are antibiotic agents.

The lactone II is also a known compound (U.S. Pat. No. 3,207,755); but there has heretofore been no means for con-. verting the lactone to the useful alcohol 1. Attempts to hydrolyze the lactone ring by conventional means, e.g., by acidic or basic hydrolysis at varying temperatures for longer periods of time, result principally in opening of the labile B- lactam ring, rather than selective lactone ring-opening. The alcohol product has thus not up to this time been obtainable from the lactone chemically in yields high enough to be adaptable to commercial production. The alcohol has been obtainable only by enzymatic hydrolysis of the acetoxy group of a compound such as 7-aminocephalosporanic acid.

The present invention, therefore, has as its principal object the provision of a method of chemically hydrolyzing the lactone of desacetyl 7-aminocephalosporanic acid (11) to desacetyl 7-aminocephalosporanic acid (I) in yields high enough to offer promise of commercial feasibility. The availability of the lactone 11 by total synthesis (French Pats. Nos.

1,480,288; 1,492,854), in conjunction with the present invention, thus enables one to produce effective cephalosporin antibiotics by a total synthesis which is adaptable to commercial 4 use.

The process of the present invention generally consists of subjecting the lactone 11, or a salt thereof, to a water-containing basic medium of pH 11-13 for about seconds to 5 minutes. The critical variables are the time and the pH. Use of longer periods of times will result in ring-opening of the B-lactam in addition to the lactone ring. Although, using the present process, some lactam ring-opening does occur, limitation of the time as stated above enables one to obtain a sufficient amount of the desired product in which the lactam ring is v intact, while the lactone ring has been hydrolyzed. The pH is i also a critical factor, since below pH 1 l, lactam-opening is extensive with little lactone-opening, and above pH 13, extensive secondary decomposition occurs.

The preferred conditions are pH 11.5-12.5 for 5-60 seconds.

The temperature of the reaction, when conducted at pH 11-13 for 5 seconds to 5 minutes should be approximately room temperature (20-30 C., preferably 25-27 C. Variation between 0-l00 C. is possible, but the optimal pH and time of reaction will be shifted.

The solvent for the reaction is not critical, provided it contains some water for hydrolysis and provided also that it dissolves the starting material. For example, aqueous alcohols, acetone, dimethylformamide, or tetrahydrofuran are satisfactory.

The reaction is most preferably conducted by dissolving a salt (including the hydrochloride, acetate, sulfate, etc.) of the lactone in water, quickly adjusting the pH to about 12 with aqueous base, and 15-30 seconds later, adding acid to pH 7 to terminate the reaction. The desired pH for the hydrolysis reaction is attained by use of such conventional basic materials as hydroxides, including sodium or potassium hydroxide; quaternary ammonium hydroxides, including ion exchange resins; and buffers capable of maintaining the desired pH.

The alcohol product may be isolated by any convenient method, since the invention resides in the particular hydrolytic conditions, rather than in any manner of isolation.

A preferred method of isolation consists of lyophilizing a mixture of the reaction solution and cellulose and then chromatographing this material on a cellulose column at 5 C., percent acetronitrile in water being the eluant. Starting material, if any remains, will be eluted first, any lactam ringopened byproductnext, and the desired hydroxy acid last. Alternatively, the product can be isolated by ion exchange chromatography. Evaporation of solvent under'reduced pressure gives. the crude product, which can be further purified by conventional means.

The following example illustrates the process of the invention, but as many variants will be obvious to those skilled in the art and thus equivalent to the process as disclosed and claimed, the example should not be construed as limiting the scope of the invention.

EXAMPLE 1 Desacetyl 7-aminocephalosporanic acid lactone, trifluoroacetatesalt (767 mg), (prepared by treating the amino lactone withtrifluoroacetic acid in the conventional manner of preparing salts) was dissolved in 50 ml. of

deoinized water (25-27 C.) and l N NaOh was added rapidly to the stirred solution until pH 12 was attained. After 15-30 seconds, the pH was adjusted to 6.8-6.9 with l N HCl, and l g. of Whatman Cellulose CF 1 1 added. The mixture was shell frozen in a bath of Dry Ice and acetone. The frozen mixture waslyophilized overnight and the residue was packed as a thin layer (5-6 mm. thick) on the top ofa column of Whatman Cellulose CF 11 (2.4 cm. X 24 cm.). The packed column was then overlayed with another layer (5-6 mm.) of cellulose and the column was;developed at 5 C. A solution of 90 percent acetonitrile in water was pumped through the column at 0.5 ml./min. to elute the components. The eluate was collected by an automaticifraction collector which changed the collecting tube every 10 min. Each fraction was analyzed by thin layer chromatography,; e.g. by spotting cellulose coated plates (EastmanKodak Co.) with a 10 A sample from each tube and developing the-plate with 75 percent acetonitrile-ZS percent water for 15 cm. Fractions 1-45 contained traces of starting material. Fractions 46-95 contained mostly the undesired (actam ring-opened byproduct. Fractions 96-151 contained a mixture of the desired product and undesired byproduct. This desired hydroxyacid product 1. The latter fractions were combined and evaporated under reduced pressure and the resulting oily mixture extracted with ethyl acetate. The remaining aqueous phase was then lyophilized overnight and the residue rinsed with percent ethyl acetate5 percent methanol. The suspension was filtered and the solid product was stored in a dessicator' at 5 C. The desired product from fractions 152-184 weighed 10 mg.; the mixture of this product and the byproduct from fractions 96-151 weighed mg.

Infrared and mass spectral analysis in comparison with an authentic sample, confirmed the identity of the desired product, which was obtained in 15-30 percent yield, based on standard bioassay methods.

EXAMPLE 2 The procedure in example 2 is the same as that described in example 1, except that the pH is adjusted to 1 1.0 and the reaction is allowed to proceed for 5 minutes. When desacetyl 7- aminocephalosporanic acid was estimated by bioassay, the conversion was approximately 10 percent.

EXAMPLE 3 The procedure in example 3 is the same as that described in example 1, except that the pH is adjusted to 1 1.5 and the reaction is allowed to proceed for 15-30 seconds. When desacetyl 7-aminocephalosporanic acid was estimated by bioassay, the conversion was approximately 15 percent.

EXAMPLE 4 The procedure is example 4 is the same as that described in example 1, except that the pH is adjusted to 13.0 and the reaction is allowed to proceed for 5-10 seconds. When desacetyl 7-aminocephalosporanic acid was estimated by bioassay, the

conversion was approximately 8 percent.

We claim:

1. A process for hydrolyzing desacetyl 7- aminocephalosporanic acid lactone to desacetyl 7- aminocephalosporanic acid comprising subjecting the said lactone in a water-containing medium to a pH of 1 1-13 for 5 seconds to 5 minutes. 

2. A process as claimed in claim 1, wherein the aqueous medium is aqueous sodium hydroxide.
 3. A process as claimed in claim 2, where the pH is from 11.5-12.5 and the time of reaction is 5-60 seconds.
 4. A process as claimed in claim 3, where the pH is 12 and the time of reaction is 15-30 seconds. 